Police gather outside Bronx Lebanon Hospital in New York after a gunman opened fire and then took his own life there on Friday, June 30, 2017. The gunman, identified as Dr. Henry Bello who used to work at the hospital, returned with a rifle hidden under his white lab coat, law enforcement officials said. (AP Photo/Mary Altaffer)

NEW YORK (AP) – Dr. Henry Bello proved a man of his word.

After he was forced to resign as a family medicine doctor amid sexual harassment allegations, he threatened his colleagues. He said he would kill them.

Law enforcement officials say Bello returned to Bronx Lebanon Hospital Friday with an AR-15 assault rifle tucked under his white lab coat and opened fire in his old department, killing one doctor and critically wounding six other people at the hospital.

They say Bello then shot himself, and staggered, bleeding, into a hallway where he collapsed and died with the rifle at his side.

Now, detectives are trying to piece together what prompted Bello to snap two years after he was forced out, and whether he was hunting for someone in particular when he went to the 16th floor and started shooting.